The ultimate goal of this effort is to develop, validate, and commercialize an ultra-broad tuning range, ultrahigh scan rate, swept laser source imaging engine that will enable the next generation of Optical Coherence Tomography / Optical Coherence Microscopy (OCT/OCM) systems. OCT and OCM enable 3D in vivo volumetric imaging of tissue pathology by detecting the echo time delay of back-reflected and backscattered light. OCT and OCM have powerful advantages as a cancer imaging modality because they provide information on tissue pathology in real time, without the need to excise and process specimens as in conventional excisional biopsy and histopathology. OCT has an axial image resolution of ~5-10 um and can image tissue over a much wider area than possible using conventional pinch biopsy. In endoscopic OCT, imaging can be performed over several square centimeters of the lumen. OCM has transverse resolutions of 1-2 um and can provide 3D image information at the cellular level. Swept source / Fourier domain OCT/OCM using compact VCSEL (vertical cavity surface emitting lasers) promises to enable imaging with significantly higher imaging speeds than existing commercial OCT technology. We propose to develop a swept source imaging engine which achieves an axial scan rate of 1 MHz, ~40x faster than commercial ophthalmic OCT instruments (25 kHz axial scan rate). Furthermore, swept source OCT/OCM using VCSEL technologies can be engineered into a compact imaging engine which is smaller than a laptop computer. The development of a high performance OCT/OCM imaging engine for the OEM market will enable access to the technology by a wide range of both established and start-up medical companies. This development strategy, which contrasts with focusing on commercialization for a single clinical application, reduces risks and will accelerate the development and impact of the technology across a broad range of clinical applications for cancer imaging. This proposed effort builds upon advances in semiconductor materials technology and tunable lasers developed by Praevium Research, Inc. in NCI grant 4R44CA101067 and follow-on commercial investment by commercial partner, Thorlabs, Inc., the world's largest manufacturer of research OCT technology. This work involves a collaboration between the primary organization Praevium Reseach, Inc. commercial partner Thorlabs, and the OCT group at the Massachusetts Institute of Technology, who was responsible for the invention and development of OCT.